The Business Secretary and a number of Lib Dem ministers were caught out making ill-judged comments to undercover reporters posing as constituents. The remarks have been seized on by Labour leader Ed Miliband as evidence that the coalition is starting to fall apart.

But Kathrine Bancroft, Cable’s former press secretary and now associate director at PLMR, expressed concern over the Telegraph’s actions. She told PRWeek: ‘They’ve got the story but there will be some cost. Aside from the aftershocks that the coalition is experiencing, the future relationship between MPs and their constituents will arguably never be quite the same again.’

She added: ‘The debate about the Telegraph’s methods has raised questions about the changing nature of broadsheet journalism and its tactics. Not only does it show how the press is still very much feeling its way around the politics of how the coalition works but is a prime example of the printed press’ need to be agenda setting in a highly competitive market.’

Before joining lobbying consultancy PLMR in October, Bancroft had the dual role of Lib Dem deputy head of media and Cable’s press secretary. After the Lib Dems entered coalition government, she became acting head of the party’s press office.

This week, Bancroft has appeared on numerous radio shows to defend her old boss. ‘Vince has always been a very candid and open politician, which is part of the reason that the nation fell in love with him in the way that they did,’ she said.

On the Telegraph’s approach, she said: ‘The fact is that the Lib Dems and the Tories are in a coalition, they are two separate parties working together and there are bound to be disagreements…. I wonder if it was worth the Telegraph taking 13 minutes of valuable constituency time.’

The Telegraph’s journalistic methods have also been called into question by newspaper pundits. Peter Preston of The Guardian and Stephen Glover of the Daily Mail both confessed to having 'qualms' about the sting operation on BBC Today programme this week. Preston said 'it was a bit of a borderline case', but suggested it could be argued that the sting was covered by a clause in the Press Commission’s code.

On the ConservativeHome website, co-editor Jonathan Isaby stated: ‘The Daily Telegraph will doubtless seek to claim that its sting has been in the public interest, but I am not convinced that abusing the privileged access to MPs afforded by the confidential arena that is the constituency surgery to entrap the MPs can be justified on that basis.’

But on the New Statesman’s website, legal correspondent David Allen Green insisted: ‘The confidentiality of the constituency surgery is there to protect the constituent, and not the MP. So, on this basis, the Daily Telegraph's secret recordings do not so far breach any grand political or legal principle.’